Electric circuit interrupter



July 20, 1943. c. THUMIM 2,324,891

ELECTRIC CIRCUIT" INTERRUPTER Filed May 1, 1941 /2 s 12 Q I y/ & /ll 1/ 1:; I m/ms W/Tl/D/fff/Pfl/T NATUHALPERwBS 5 O 23 VASE/9770 m Fig. 5 W Ih N m 1 x 14- '12 g v \r v M v i 7/ f j Tim 3 Tim i-u'u 0 Z :5 "3145c 2/ 48: a

Inventor: Carl ThLLmiT-m is Attorne Patcntcd July 210, 1943 ill iTED STATES PATENT OFFICE ELECTREC CERCUKT ZN'EERRKJPTER Carl ihumim, Yeadon, Pa, assignor to Generai Electric Company, a corporation oi"- New York Application May 1, liiil, Scriai No. 3%,381

4 Claims. (Cl. 200146) My invention relates to electric circuit interrupters more particularly to those of the heavy-duty type ior and breaking a highvoltage power circuit.

High-voltage circuit breakers are usually reouired to break the circuit under heavy-current conditions and often such operation causes deterioration and burning of the contacts, that is, an are forms at the coasting contact surfaces before substantial contact pressure is established, thereby causing melting of the contact material with a resultant formation of high-resistance oxides and the gradual deterioration of the contacts themselves. Contacts for circuit breakers of this type are often of the so-called butt type" and generally include an arcing contact and a main current-carrying contact. It would be de sirable to provide a butt contact arrangement for carrying heavy currents which provides r lative movement between the contacting portions of the contacts after engagement thereof so as to break down any oxides or the like. Also, since the trend of modern switchgear has been toward higher and higher speeds of circuit breakers, it would be desirable further to provide a contact structure for a circuit breaker which will permit high-speed circuit interruption.

Accordingly, it is an object of my invention to provide a new and improved contact structure for an electric circuit breaker in which relative movement between the contacting portions of a butt contact are obtained after engagement of the relatively movable portions thereof.

It'is another object of my invention to provide a high-speed circuit breaker having a new and improved butt contact provided with an arcing portion and a main current-carrying portion.

It is a further object of my invention to provide a. new and improved high-speed circuit breaker provided with a butt contact having cur-- rent-carrying and arcing contact portions in which the transfer of a current from the main current-carrying contact to the arcing contact is facilitated and in which the loop effect of the current tends to keep the contacts closed.

Further objects and advantages of my invention will become apparent as the following de scription proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the c aims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is an elevational view of the coacting contact structure of an oil circuit breaker embodying the present invention; Fig. 2 is an end view of the contact structure shown in Fig. l, and Figs. 3 and l are views similar to Fig. 1 showing successive positions of the contact portions during the circuit-closing operation.

The circuit breaker illustrated in the drawing is of the well. known oil immersed type although it should. be understood that the present invention is equally applicable to air circuit breakers. In the specific embodiment shown in the drawing, the relatively movable contact structure comprises a pair of stationary terminals or breaker studs iii, only one of which is shown in the drawing since the other is identical therewith, which is connected to a stirrup-shaped structure 5 i for supporting the fixed contact structure to be described hereinafter. The breaker terminals or studs it are insulated from the circuit-breaker structure by an insulating bushing means l2. The fixed contact structures,

only one of which is shown. in Fig. 1, are adapted to be bridged by a bridging member l3 to provide the well-known loop circuit which has become more or less conventional in oil-immersed circuit breakers. The bridging member i3 is provided with the usual insulating lift rod I4 for operating bridging member it in reciprocal vertical movement between the closed and open circuit positions. The bridging member i3 provides a movable conducting element and is provided at either end thereof with a butt contact surface it, a portion of which is preferably formed of an arc-resistant material !6, the purpose of which will become apparent as the following description proceeds.

The stirrup or stationary conducting element H is arranged to support on pivot pin i! one or more auxiliary conducting member i 8 each having an elongated or slotted opening I'B therein for cooperating with pivot member ll. Each auxiliary conducting member i8 is provided with an arcing contact portion i822. preferably formed of an arc-resistant material and a main currentcarrying portion i811. The arcing contact portion E85. and the main current-carrying portion lfib of auxiliary conducting member iii are arranged on either side or slotted opening l9. Auxiliary conducting member i8 is also provided with an extension E which is electrically connected to stirrup i l by means of flexible lead 20 so as to provide efficient conduction of high currents between auxiliary conducting member l8 which forms one portion of the butt contact and circuit breaker terminal or stud It. In order to insure engagement of arcing contact portion We of auxmovement of bridging member iliary conducting member l8 with the butt contact surface [5 of bridging member l3 prior to the engagement of the main current-carrying portion 18s, I provide suitable resilient means, such as spring 2!, which is supported between spring guide 22 suitably mounted on stirrup H and spring guide 18d which is illustrated as an integral portion of auxiliary conducting member-l8. It will be understood by those skilled in the art that fixed spring guides 18d and 22 might be replaced by pivoted spring supports in order to avoid sidewise bending of spring means 2!. By this arrangement, the arcing contact portion its had a lead as indicated in Fig. 1, over the main current-carrying contact portion during the circuit-closing operation and 9. corresponding lag a: during the circuit-opening operation.

Spring guide 18d is placed closely adjacent the long axis of slotted opening I9, which is vertical in the position shown in Fig. 1, but between this axis and the arcing contact portion I88 in order normally to bias auxiliary conducting member IS in a clockwise direction about pivot member l? as viewed in Fig. 1 so as to engage the stop member 23 supported by stirrup H. By this arrangement, it will be observed that the arcing contact portion IBa of the butt contact is the first to engage and the last to disengage with the cooperating butt contact surface I of bridging member l3.

Preferably, whena plurality of auxiliary conducting members l8 are provided for each contact structure, it is desirable that the spring means 2| associated with the respective auxiliary members have different gradients so as to provide different natural periods of vibration, thereby to eliminate simultaneous bouncing of all of the auxiliary conducting members or fingers as disclosed and claimed in United States Letters Patent, 2,185,166, granted December 26, 1939, upon an application of Ralph E. Bold, and assigned to the same assignee as the present application.

The operation of the contact structure embodying my invention can best be understood by reference to Figs. 1, 3, and 4. Fig. 1 discloses bridging member i3 shortly before arcing contact portion i8a engages with the butt contact surface i5 thereof. After engagement of the arcing contact portion 8a of auxiliary conducting member [8 with the butt contact surface l5 of bridging member 13, auxiliary conducting member 48 will tend to rotate about pivot member I? so that main current-carrying portion IBb tends to move toward bridging member 93, and consequently the bridging member I3 is required to move a distance somewhat less than the distance a: of Fig. 1 before the current-carrying portion 98b makes contact with the cooperating butt contact surface l5. Fig. 3illustrates bridging member it in solid lines at the instant when engagement of the main current-carrying con" tact 18b and the contacting surface l5 of bridging member 13 occurs. Bridging member I3 is also indicated in dotted lines in Fig. 3 at the instant of engagement of arcing contact portion I83 with butt contact surface 15 of bridging member 13. The distance y between these two positions is considerably less than :n as may be seen by comparison with Fig. 1. It will be understood by those skilledinthe art that, during the circuit-opening operation, the reverse will be true and, consequently, the current-carrying contacts will separate faster than the I3 due to the fact that the lag in the disengagement or" the arcing contact portion is over the main current-carrying contact portion its is less than the stroke of bridging member l3 during this interval. By this arrangement, high-speed make and break of the current-carrying contacts are provided.

When both the arcing contact and currentcarrying contact portions '88 and I81; are engaged with the butt contact surface 15 of bridging member 13, the axis of slot I9 ,is no longer vertical as in Fig. 1 so that further movement of bridging member I3 in the upward direction will cause pivot pin H to move in slot ill to produce relative movement .between the engaging portions of the butt contact. The extent of this movement is shown by the distance w in Fig. 4. This sliding action of a butt contact after engagement thereof eliminates the efiects of any oxides and insures a very efiicient contact. It will be observed in Fig. 4, that, in the closed position of the circuit breaker, spring means 2| no longer tends to cause clockwise rotation of auxiliary conducting member i8 but, distributes its force between 8a and We with the larger proportion on lSb to maintain closure of the current-carrying portion of the butt contact.

The auxiliary conducting member i8 is arranged to facilitate transfer of current from the main contacting portion to the arcing contacting portion, both by the magnetic efiect of the current loop, as is well understood by those skilled in the art, and secondly by the fact that the conducting path from portion I to portion lBb is longer than the conducting path from 52c to We. Also by the arrangement described above, the magnetic loop effect of the current produces a force tending to maintain the main currentcarrying contacts in the closed position.

It should be understood that my invention is not limited to the specific details of construction and arrangement thereof herein illustrated and that changes and modifications may occur to one skilled in the art without departing from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a contact structure for an electric circuit interrupter, a stationary conducting element, a movable conducting element, means pivotally supported by one of said conducting elements including an arcing contact and a main current-carrying contact so constructed and arranged with respect to said conducting elements as to provide a butt contact, and means including a slotted opening in said first-mentioned means for producing relative movement between the cooperating parts of said butt contact after engagement of such parts, whereby an efficient contact is insured.

2. In a contact structure for an electric circuit interrupter, astationaiy conducting element a movable conducting element, a plurality of auxiliary conducting members pivotally supported by one of said conducting elements each including an arcing contact portion and a main current-carrying contact portion, and a plurality of spring means,.one for each of said auxiliary conducting members to cause said arcing contact portions to have a predetermined lead over said main current-carrying contact portions during the circuit-closing operation of said circuit interrupter, said spring means being characterized by diiierent natural periods of vibration.

3. An electric circuit interrupter comprising a pair of relatively movable conducting elements, an auxiliary conducting member, means including a slotted opening in said auxiliary conducting member for pivotally supporting said member on one of said relatively movable elements to produce a butt contact for engaging the other of said elements, said auxiliary conducting member having an arcing contact portion and a main current-carrying contact portion, spring means tending to cause said arcing contact portion to engage said other element before said current-carrying contact portion engages said other element during the circuit-closing operation, and means including said slotted opening in said auxiliary conducting member for producing relative movement between the contacting portions of said butt contact after engagement of both said arcing contact portion and ducting member for pivotally supporting said member on one of said relatively movable elements to produce a butt contact for engaging the other of said elements, said auxiliary conducting member having an arcing contact portion and a main current-carrying contact portion, spring means tending to rotate said auxiliary conducting member about'its support in order to cause said arcing contact portion to engage said other element before said currentcarrying contact portion engages said other element during the circuit-closing operation, stop means supported by saidone element for determining the lead of said arcing contact portion over said current-carrying contact portion during said circuitclosing operation, and means including said slotted opening in said auxiliary conducting member for producing relative movement between the contacting portions of said said current-carrying contact portion with said 20 butt contact after engagement of both said other conducting element.

4. An electric circuit interrupter comprising a pair of relatively movable conducting elements, an auxiliary conducting member, means including a slotted opening in said auxiliary conarcing contact portion and said current-carrying contact portion with said other conducting element.

CARL THUMIM. 

